This invention relates generally to optical absorption spectroscopy, and more specifically relates to the optical absorption cells utilized in such environments for containing the samples which are subjected to analysis.
In the practice of optical absorption spectroscopy, apparatus such as spectrophotometers are utilized, which include one or more optical paths in which sample or reference materials are inserted, in order that the light absorption characteristics of the materials may be evaluated. The materials to be thus analyzed are physically contained in an optical absorption cell, which typically comprises a small rectangular container, the opposed sides of which are relatively transparent to the wavelengths being utilized during analysis.
Depending upon the nature of the sample being analyzed it is frequently required that agitation be provided within the absorption cell, in order to maintain a high degree of uniformity. A common arrangement that has been utilized in the past to enable such result, incorporates so-called magnetic stirrers. According to this well-known arrangement, a magnetically responsive agitator is positioned at the bottom of the cell container and is caused to rotate in synchronism with a rotating magnetic field provided beneath the cell, e.g. by a rotating bar magnet.
The dimensions of many typical optical absorption cells are such that the cell is relatively oblong, e.g. the cell container may typically have a height of 4 to 5 centimeters, and a transverse cross-section of perhaps 1 centimeter by 1 centimeter. Particularly in configurations of this type, magnetic stirrers of the aforementioned type are relatively ineffective in providing good mixing. This type of problem is especially significant where the liquid present in the cell is of relatively high viscosity, or if it is required (in accordance with the material being analyzed) to maintain heavy particles suspended in the liquid. Under the type of conditions cited, the stirring tends to occur only in the lower one-third to one-half of the cell, whereas the upper one-half to two-thirds of the cell may remain in good part, undisturbed.
In accordance with the foregoing it may be regarded as an object of the present invention, to provide an improved optical absorption cell, wherein magnetic stirring is effective to provide excellent and relatively complete intermixing of the fluids contained within such cell, including excellent agitation of such materials as may be suspended within such fluid.
It is a further object of the invention to provide an optical absorption cell utilizing magnetic stirring, wherein excellent agitation of the cell contents is assured throughout the entire volume of such cell, even when such cell is of a relatively elongated configuration.